Estimation of Groundwater Recharge under various land ... - RMZ

190 Purandara B. K., Venkatesh B. & V. K. Choubeyface and layer between 120–150 cm,as these controls the runoff process. Asignificance level of 0.01 was used totest differences between specific pairsof sites. However, results indicatedthat, both F-test (F < 0.001) and LeastSignificant Difference was significantat this level.The measured saturated hydraulic conductivitiesare plotted as box plots toview the variation within the measuredvalues. The length of the box reflectsthe inter-quartile range, and the fence ortails of the box plots are marked by theextremes if there are no outliers, or elseby the largest and smallest observationthat does not qualify for an outlier. Theoutliers are defined as data points morethan 1.5 times the inter-quartile rangeaway from the upper or lower quartile.The middle horizontal bar on the boxplot represents the median of the data.The saturated hydraulic conductivityobserved for soils in the undisturbedforests and also in afforested regionsis comparatively higher in the lateriticsoils, followed by red soil and least isobserved in black cotton soils (Figure2). Another set of data observed acrossan array of land use types, showed thatthe saturated hydraulic conductivityis maximum in forest and plantations(afforested land). Minimum saturatedhydraulic conductivity was observed indegraded forests. However, saturatedhydraulic conductivity in afforested re-gion depends upon both soil type andalso the type of plantation, such as teak,causarina or Acacia. A diagrammaticrepresentation of the variation in saturatedhydraulic conductivity with landuse type is shown in Figure 3. Similarobservation was made by Venkateshet al. (2004) for Barchi watershed ina plateau region. It is reported that inregions afforested with teak plantationhas the lowest K svalue as compared tothe forest and degraded lands.The computed rainfall intensities fordifferent frequencies are superimposedon these box plots to identify the possiblerunoff generation mechanism.From the Figure 2 it is evident that, thered and lateritic soils are more permeablethan the black soils. However, inblack soils, the mean Ks are exceededby the rainfall intensities even at 1 in 1year and above, indicating the dominationof infiltration excess overland flow(Hortonian overland flow) occurrences.The box-plot.3, depicts that, the naturalforest and acacia plantation are comparativelyhas higher permeability than theother land-uses considered for the analysis.From the box-plot, it is observedthat, the K svalues in natural forest aremuch higher than the rainfall intensitiesat 1 in 50 years, indicating that in suchregions the probability of having Hortonianoverland flow is rare. However,Putty et al. (2000) reported the pipeflow phenomenon in such conditions.RMZ-M&G 2010, 57